1. Field of the Invention
This invention relates to the field of information networks, and more particularly relates to detecting errors in network elements that route information through such information networks.
2. Description of the Related Art
Today's networks carry vast amounts of information. High bandwidth applications supported by these networks include streaming video, streaming audio, and large aggregations of voice traffic. In the future, these bandwidth demands are certain to increase. This information must be quickly and efficiently distributed to various destinations without the introduction of errors. Many modem networking topologies employ a switching matrix of some kind to perform this function.
For example, certain networks employ a point-to-point topology in which each node is coupled to another node by one or more connections. The easiest way to interconnect a group of N nodes is by using an N×N crossbar switch. One advantage is that such a scheme is strictly non-blocking. This means that a connection can be made between any unused input and any unused output, regardless of the current state of the switch. Thus, the switch can be reconfigured at any time without introducing errors in the pre-existing information streams (i.e., connections). This is an important capability in many applications, such as data networks (e.g., errors causing retransmission of the damaged data and so reducing available bandwidth) and telephony networks (e.g., dropped telephone calls). However, N×N crossbar switches grow exponentially as connections are added, meaning that N2 switches are required to build a network having N inputs and N outputs. Alternatively, such connections can be configured using one of a number of multi-stage interconnection network (MIN) architectures. MIN architectures can generally be divided into three classes: blocking, rearrangeably non-blocking, and strictly non-blocking.
A blocking network is characterized by the property that there is only one path from any input to any output. Because some of the paths share one or more links within the MIN, a high number of permutations cannot be routed when using such networks. A rearrangeably non-blocking network allows idle pairs of input and output ports to be connected after possibly rearranging some of the existing connections (i.e., reconfiguring the switching matrix), although information carried on some or all of the existing connections may experience errors during the switching matrix's reconfiguration. A strictly non-blocking network allows any idle pair of input and output ports to be connected without having to rearrange any of the existing connections without errors being experienced on the existing connections, regardless of the current state of the network.
However, as in any information system, errors can occur in the data streams switched by the switching matrix employed. Left undetected, such errors can cause signal degradation and interruptions. This is of particular importance in real-time applications such as telephony and streaming video, where such signal degradation and interruptions are especially noticeable to the users of such systems. Thus, such errors should be detected quickly and accurately to maintain the quality of such signals.